bpo-32381: Fix PyRun_SimpleFileExFlags() encoding (GH-23642) (GH-23692) (GH-23696)

bpo-32381: Fix PyRun_SimpleFileExFlags() encoding (GH-23642) (GH-23692) (GH-23696)

Fix encoding name when running a ".pyc" file on Windows:
PyRun_SimpleFileExFlags() now uses the correct encoding to decode the
filename.

* Add pyrun_file() subfunction.
* Add pyrun_simple_file() subfunction.
* PyRun_SimpleFileExFlags() now calls _Py_fopen_obj() rather than
  _Py_fopen().

(cherry picked from commit b6d98c10fff6f320f8fdf595c3f9a05d8be4e31d)
(cherry picked from commit f0e42ae03c41ec32fcb3064772f46ff7f2c5ff3b)